function Shape() {
	this.name = 'Shape';
	this.toString = function (){
		return this.name;
	};
}
function TwoDShape(){
	this.name = '2D shape';
}
function Triangle(side , height){
	this.name = 'Triangle';
	this.side = side;
	this.height = height;
	this.getArea = function(){
		return this.side * this.height / 2;
	};
}
TwoDShape.prototype = new Shape();
Triangle.prototype  = new TwoDShape();
TwoDShape.prototype.constructor = TwoDShape;
Triangle.prototype.constructor = Triangle;
var my = new Triangle(5,10);
console.log("my.getArea()");
console.log(my.getArea());